Abstract [en]

BACKGROUND: Ankylosing spondylitis (AS) is a rheumatoid disease leading to progressive ossification of the spinal column. Patients suffering from AS are highly susceptible to unstable vertebral fractures and often require surgical stabilisation due to long lever arms. Medical treatment of these patients improved during the last decades, but until now it is unknown whether the annual number of spinal fractures changed during the last years. Since the annual count of fracture is an effective measure for efficacy of injury prevention and patient safety in AS patients, the current recommendations of activity have to be revised accordingly.

METHODS: Data for all patients with AS treated as inpatients between 01/01/1987 and 31/12/2008 were extracted from the Swedish National Hospital Discharge Registry (SNHDR). The data in the registry are collected prospectively, recording all inpatient admissions throughout Sweden. The SNHDR uses the codes for diagnoses at discharge according to the Swedish versions of the International Classification of Diseases (ICD-9 and ICD-10).

RESULTS: During the years from 1987 to 2008 17,764 patients with AS were treated as inpatients; of these 724 patients were treated due to spinal fractures. The annual number of cervical, thoracic and lumbar fractures in the registry increased until 2008 (r = 0.94).

CONCLUSIONS: Despite the improved treatment of AS the annual number of vertebral fractures requiring inpatient care increased during the last two decades. Possible explanations are population growth, greater awareness of fractures, improved diagnostics, improved emergency care reducing fatalities, and a higher activity level of patients receiving modern medical therapy. Obviously the improvement of medical treatment did not reduce the susceptibility of these patients to unstable fractures. Thus the restrictive injury prevention recommendations for patients with AS cannot be defused, but must be critically revised to improve patient safety.

Abstract [en]

Background: Spinal fractures related to ankylosing spondylitis (AS) are often associated with serious complications. Therefore, knowledge of the incidence, best treatment, outcome, and prevention would assist in improving current guidelines.

Objectives: This thesis aims at (1) analysing the complications and mortality of surgical treatment, (2) mapping the incidence and treatment modalities for these patients in Sweden, as well as (3) investigating the putative preventive effect of biological disease modifying anti-rheumatic drug (bDMARD) therapy on spinal fractures related to AS.

Methods: Merged multiple national registries were used to identify predictors of mortality and spinal fractures in patients with AS. Beyond that a finite element model (FEM) was designed to simulating a cervicothoracic fracture related to AS.

Results and Conclusions: During the last two decades an increase of the incidence of vertebral fractures in patients with AS was observed. With the introduction of bDMARD treatment of AS was revolutionised and quality of life and function improved. It seems that the improved quality of life and function in these patients does not correlate with a reduced fracture risk. Still, for the first time a beneficial effect of bDMARD with regard to spinal fracture occurrence was provided. The risk of spinal fractures was not reduced, but the debut of a spinal fracture was delayed with bDMARD. Since for this study the observation interval was only a decade, a future follow-up should revisit the effect of bDMARD on spinal fractures related to AS.

Furthermore, it was shown that posterior stabilisation is an effective method for restoring stability without the necessity of additional external fixation. Most likely the early rehabilitation reduced pulmonary complications, which in turn reduced early mortality of these fractures. The FEM could be used to identify the most appropriate implant configuration, since no well-established cadaver models exist.